U.S. Pat. Nos. 5,005,647 and 5,005,648 assigned to the present assignee teach the treatment of subterranean earth formations in cased well boreholes by injecting under hydraulic or gravity pressure a treating fluid comprising a polymerizable material which can be acid catalyzed to cure or set in a period of from 1 to 16 hours at formation conditions. The single step injection is performed with the treating fluid which (for high temperature use) contains an oligomer or monomer of furfuryl alcohol, an ester such as ethyl or butyl acetate and a catalyst such as orthonitrobenzoic acid or toluene sulfonic acid in a concentration of from 1% to 4% by weight which is selected to produce a set time at formation temperature in the range of 1 to 16 hours. These are taught in detail in the above referenced two U.S. patents which are incorporated herein by reference for all purposes.
A great number of successful well treatments have been made according to the teachings of the referenced patents. However, a persistent problem which has arisen in some wellbore environments in the placement of such liquid resins for treating formations for water, gas or sand shutoff, has been the excessive leakoff of treating fluid encountered within an interval that has a high permeability zone or a large void space such as exists in a "washed out" region near the borehole. In this environment a large volume of relatively expensive resin can leak off into the unexpected high permeability zone or void prior to the resin setting. This can require repeat treatments to completely cure the problem of water, gas or sand shutoff.
Accordingly, in spite of the successes of the referenced prior patented methods, there is still a substantial unfulfilled need for an inexpensive, simple and reliable procedure which can be applied to wellbore formations in which a high permeability zone or washed out or void region exists near the borehole for shutting off water from a water producing interval, gas from gas producing intervals, for plugging leaks in well casing or flow channels in cement around the casing using a polymerizable composition, and for reducing the cost of such treatment.